The present invention relates to a keyswitch structure used for the key input of compact electronic computers, or calculators, etc.
Conventionally, a keyswitch used for the data input of a small electronic calculator has a construction as shown in FIG. 1, for example. In the keyswitch of this construction, the head portion of a key button 1 is inserted into a button hole 2a in an upper case 2 from the inside thereof and is prevented from slipping off by its collar portion 1a. The key button 1 is elastically held so that the collar portion 1a is brought into contact with the peripheral edge of the button hole 2a of the upper case 2 by a protruding portion 3a which protrudes upward from an elastic sheet 3 underlying the key button 1. A substrate 4 formed of a flexible film sheet and a circuit board 5 are arranged under the elastic sheet 3. A fixed contact 5a on the under surface of the substrate 4 and a movable contact 4a on the top surface of the circuit board 5 face each other with a spacer 6 between them. The spacer 6 has an opening 6a which corresponds in position to the key button 1. The elastic sheet 3, the substrate 4, the spacer 6, and the circuit board 5 are immovably fixed to retaining portions 2b of the upper case 2 by a lower case 7. If the key button 1 is pushed down, the protruding portion 3a is depressed, so that a push portion 3b inside of the protruding portion 3a forces down the substrate 4. As a result, the movable contact 4a is brought into touch with the fixed contact 5a of the circuit board 5 inside the opening 6a of the spacer 6, and an input signal is produced. When the key button 1 is released, the protruding portion 3a of the elastic sheet 3 is automatically restored to force up the key button 1; and the flexible substrate 4 is restored to its original flat form so that the movable contact 4a is separated from the fixed contact 5a. Thus, a key input operation is ended.
Constructed in this manner, the prior art keyswitch requires many components and is therefore low in production efficiency. Automatic assembly of so many sheetlike components using a vacuum system or other system would require large-scale equipment, resulting in a cost increase. Moreover, there are some restrictions on the manufacturing of an extra thin apparatus.